The invention relates generally to training techniques for multiple-antenna communications.
An effective approach to increasing the data rate as well as the power efficiency over wireless channels involves introducing temporal and spatial correlation into signals transmitted from different antennas. A multiple-antenna communication system can achieve very high data rates with low error probabilities, in particular when the receiver has knowledge of the wireless channel response. For noncoherent channels, training-based schemes are generally employed, in which known signals (pilots) are periodically transmitted for the receiver to learn the channel. The transmission consists of two phases, namely, a training phase and a data transmission phase. In the training phase, the transmitter dedicates TT time intervals out of a total T coherent intervals for transmitting pilot symbols.
For conventional training-based schemes, no information is sent during the training period. This may lead to low spectral efficiency, especially for high-rate communications with a short coherent interval. For delay-limited channels with a finite SNR, conventional training-based schemes may not be optimal.